Archive | January, 2011

Gender Identity – Milkweed Bugs

31 Jan
Ventral views of male and female milkweed bugs (College Station, Texas).

Distinguishing markings on the abdomens of a female and male milkweed bug (Lygaeidae: Oncopeltus fasciatus).

So one random factoid I encountered while researching milkweed bugs last week is that you can distinguish males and females by the markings on the underside of their abdomens.  Females have a black stripe and two black dots, while males (the smaller sex) have two black stripes.  I didn’t have a male to draw comparisons against last week, so I tracked down a neighboring lab colony of milkweed bugs and sure enough, boys and girls!  (Thus resolving any future crises I may have involving the gender identification of milkweed bugs.)

I had originally wanted to photograph a mating pair, but apparently they found being repeatedly flipped onto their backs disruptive.  I finally resorted to sticking them in the freezer for a few minutes, after which they gave a very good impression of being dead (slightly too good an impression).  Luckily they eventually perked back up and I got a few photos.

Milkweed Bugs

28 Jan
A female milkweed bug (College Station, Texas)

A female milkweed bug (Lygaeidae: Oncopeltus fasciatus)

I love Texas–when I’m not complaining about the heat–because you can find insects virtually year round.  In December I was playing with earwigs and now it’s January and already the fire ant mounds are popping up everywhere like spring flowers.  (Working with fire ants has severely warped my perceptions of this event.)  I found this large milkweed bug (Oncopeltus fasciatus) sunning itself today in the balmy 70 degree weather. lists these fellows as active only from May to October, at least in North Carolina, which is apparently because North Carolinians have an odd phenomenon known as ‘seasons.’

Ventral view of a female milkweed bug (College Station, Texas)

Ventral view of a female milkweed bug (Lygaeidae).

Milkweed bugs belong to the true bug family Lygaeidae, the seed bugs.  Like other members of the family, milkweed bugs make their living feeding on nutrient rich plant seeds, in this case usually the seeds of the eponymous milkweed plant.  (Yes, this entire previous sentence was an excuse for me to use the word ‘eponymous’.)  They use their tubular mouthparts to pierce the walls of seed pods, feeding on the seeds within.

Like that other famous milkweed feeder, the monarch butterfly, the bright, warning coloration of milkweed bugs warns predators that these bugs sequester toxic compounds from the plant in their bodies, making them distasteful.  Milkweed bugs can be fed a variety of other seeds, although interestingly they habituate to food types and it often takes several generations for them to make a switch.  Milkweed bugs in the lab are generally fed sunflower seeds, shelled or cracked since their mouthparts can’t pierce the harder husks.

A day in the life of a butterfly

24 Jan

A story in three parts.

Part 1.

A skipper perched on a yellow flower.

Part 2.

A skipper mysteriously under a yellow flower.

Part 3.

A skipper ambushed by a spider under a yellow flower.

The End.

The effect of children on mantises

21 Jan
Close up on the head, eyes, and mandibles of a Carolina mantis.

Close up of a Carolina mantis (Stagmomantis carolina).

Another close up.  This is a Carolina mantis I’ve been raising for a while.  Recently I took her along to an outreach program where we had a live insect zoo, and the kids got a huge kick out of seeing and holding a preying mantis.

Unfortunately, the mantis apparently found a pack of excited 6th grade girls a bit unnerving, and I had to put her back in her container when she started flashing her yellow hindwings in a threat display.  I have never actually managed to get a mantis to do a display for me, so it was actually pretty interesting.  Moreover, weeks later I still couldn’t come near her container without being the recipient of an immediate threat display.  (Small children are apparently just that unsettling.)

I had meant to take a picture for the blog, but Christmas break has apparently soothed her nerves sufficiently that she can be handled again without instant mantis-freak-out.

Spider Fur

17 Jan
Close up of wolf spider head.

Close up of wolf spider head (Lycosidae).

I’ve been playing around with extreme close ups.   It’s been fun!  In these pictures, you can really see the combination of “hair” types that give wolf spiders their furry, wolf-like appearance.  Vibrations of these hairs help the spiders sense the movement of their prey, while other hairs contain chemoreceptors that let them ‘taste’ airborne odors.  Meanwhile, the hairs on a female wolf spider’s abdomen also have special spines and knobs, to help her babies keep their grip while they ride in safety.

Wolf spider close up of abdomen.

Close up of wolf spider abdomen.

Soft and Fluffy – Flannel Moths and Puss Caterpillars

14 Jan
A fluffy megalopygid moth rest on a leaf at night (Welder Wildlife Refuge, TX).

A flannel moth rests on a leaf (Megalopygidae).

I found this fluffy little moth resting on a leaf near a light at the Welder Wildlife Refuge.  The soft, fuzzy appearance of the moths gives them their common name, flannel moths (Megalopygidae).  These moths are probably best known for their strange, furred looking caterpillars (called asps or puss caterpillars) which can deliver a painful, long-lasting sting with the venomous spines hidden under their soft furry countenance.  The cocoons of these moths have an interesting trap-door style “lid”, which allows an easy emergence for the adult moth.

Skin Wings — Earwig wing folding

10 Jan
The wing folding of the common earwig (Forficulidae).

The wing folding of the common earwig (Forficulidae).

Just a quick set of pictures I threw together while I was practicing my wing spreading techniques.  Earwigs are tricky because their hind wings are so delicate, as well as compactly folded.  In earwigs the hind wings are hidden under the short tough forewings (tegmina) and may be folded up to 40 times.  Earwigs can actually use their pincers to help them fold up their wings like insect origami  You can see some of the fan folding in the third picture.  For some reason the wings also seemed to want to twist upside down on me.

The order name Dermaptera means “skin wings” and refers to the leathery texture of the forewings.  I was surprised to learn earwigs had wings when I started studying entomology, because the common species we have locally is secondarily wingless in the adult form.

The Common Earwig

7 Jan
Male earwig (Forficulidae) in leaf litter.

Male earwig in leaf litter (San Diego, California).

Here’s some more shots of the earwigs I came across flipping stones during the ESA conference in San Diego.  We mostly only see the small, wingless Anisolabididae in my area so I was unreasonably impressed and excited by these common or european earwigs (family Forficulidae).  Nonetheless, these are interesting little insects to take a closer look at.  Aside from the females guarding eggs and nymphs, it was also interesting to observe the range in sizes of the cerci, which are adapted into pincers in earwigs.  Starting with the short straight pincers of the female earwigs, these cerci ranged from similarly sized but curvier pincers in the males to large curved scimitars nearly twice as long.

The cerci of male and female common earwigs (Forficulidae).

Male and female common earwigs (Forficulidae).

These earwigs are fairly easy to handle, being generally unaggressive towards humans.  When threatened, they may attempt to pinch with their cerci, but rarely have enough of a grip to do any damage.  However, I did manage to acquire a war wound while playing with these fellows.  One of the males caught my finger in a particularly vicious pinch and actually drew blood with his cerci.  Since my brain has been warped by entomology I reacted by being impressed and interested.  I went around showing my finger to my fellow entomologists and asking if they knew earwigs could do that (they were universally surprised).

Of course, I took the moral of the story not to be “don’t handle earwigs” but more of a “be careful with sharp objects.”  Even peaceful cicadas have been known to get in a chance stab with their proboscises.  On the whole I’ve found it’s much more useful (and entertaining) to know where the sharp bits are and how to avoid them.

Male common earwig on hand (Forficulidae).

A male earwig held in hand.